Assessing changes in regional cerebral hemodynamics in adults with a high-density full-head coverage time-resolved near-infrared spectroscopy device

Significance

Cerebral oximeters have the potential to detect abnormal cerebral blood oxygenation to allow for early intervention. However, current commercial systems have two major limitations: (1) spatial coverage of only the frontal region, assuming that surgery-related hemodynamic effects are global and (2) susceptibility to extracerebral signal contamination inherent to continuous-wave near-infrared spectroscopy (NIRS).

Aim

This work aimed to assess the feasibility of a high-density, time-resolved (tr) NIRS device (Kernel Flow) to monitor regional oxygenation changes across the cerebral cortex during surgery.

Approach

The Flow system was assessed using two protocols. First, digital carotid compression was applied to healthy volunteers to cause a rapid oxygenation decrease across the ipsilateral hemisphere without affecting the contralateral side. Next, the system was used on patients undergoing shoulder surgery to provide continuous monitoring of cerebral oxygenation. In both protocols, the improved depth sensitivity of trNIRS was investigated by applying moment analysis. A dynamic wavelet filtering approach was also developed to remove observed temperature-induced signal drifts.

Results

In the first protocol (28 ± 5 years; five females, five males), hair significantly impacted regional sensitivity; however, the enhanced depth sensitivity of trNIRS was able to separate brain and scalp responses in the frontal region. Regional sensitivity was improved in the clinical study given the age-related reduction in hair density of the patients (65 ± 15 years; 14 females, 13 males). In five patients who received phenylephrine to treat hypotension, different scalp and brain oxygenation responses were apparent, although no regional differences were observed.

Conclusions

The Kernel Flow has promise as an intraoperative neuromonitoring device. Although regional sensitivity was affected by hair color and density, enhanced depth sensitivity of trNIRS was able to resolve differences in scalp and brain oxygenation responses in both protocols.

Cerebral Oximetry During Pediatric In-Hospital Cardiac Arrest: A Multicenter Study of Survival and Neurologic Outcome

OBJECTIVES

To determine if near-infrared spectroscopy measuring cerebral regional oxygen saturation (crS o2 ) during cardiopulmonary resuscitation is associated with return of spontaneous circulation (ROSC) and survival to hospital discharge (SHD) in children.

DESIGN

Multicenter, observational study.

SETTING

Three hospitals in the pediatric Resuscitation Quality (pediRES-Q) collaborative from 2015 to 2022.

PATIENTS

Children younger than 18 years, gestational age 37 weeks old or older with in-hospital cardiac arrest (IHCA) receiving cardiopulmonary resuscitation greater than or equal to 1 minute and intra-arrest crS o2 monitoring.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Primary outcome was ROSC greater than or equal to 20 minutes without extracorporeal membrane oxygenation. Secondary outcomes included SHD and favorable neurologic outcome (FNO) (Pediatric Cerebral Performance Category 1-2 or no change from prearrest). Among 3212 IHCA events (index and nonindex), 123 met inclusion criteria in 93 patients. Median age was 0.3 years (0.1-1.4 yr) and 31% (38/123) of the cardiopulmonary resuscitation events occurred in patients with cyanotic heart disease. Median cardiopulmonary resuscitation duration was 8 minutes (3-28 min) and ROSC was achieved in 65% (80/123). For index events, SHD was achieved in 59% (54/91) and FNO in 41% (37/91). We determined the association of median intra-arrest crS o2 and percent of crS o2 values above a priori thresholds during the: 1) entire cardiopulmonary resuscitation event, 2) first 5 minutes, and 3) last 5 minutes with ROSC, SHD, and FNO. Higher crS o2 for the entire cardiopulmonary resuscitation event, first 5 minutes, and last 5 minutes were associated with higher likelihood of ROSC, SHD, and FNO. In multivariable analysis of the infant group (age < 1 yr), higher crS o2 was associated with ROSC (odds ratio [OR], 1.06; 95% CI, 1.03-1.10), SHD (OR, 1.04; 95% CI, 1.01-1.07), and FNO (OR, 1.05; 95% CI, 1.02-1.08) after adjusting for presence of cyanotic heart disease.

CONCLUSIONS

Higher crS o2 during pediatric IHCA was associated with increased rate of ROSC, SHD, and FNO. Intra-arrest crS o2 may have a role as a real-time, noninvasive predictor of ROSC.

Impact of Skin Pigmentation on Cerebral Regional Saturation of Oxygen Using Near-Infrared Spectroscopy: A Systematic Review

OBJECTIVES

Near-infrared spectroscopy (NIRS) is used in critical care settings to measure regional cerebral tissue oxygenation (rSo2). However, the accuracy of such measurements has been questioned in darker-skinned individuals due to the confounding effects of light absorption by melanin. In this systematic review, we aim to synthesize the available evidence on the effect of skin pigmentation on rSo2 readings.

DATA SOURCES

We systematically searched MEDLINE, Cochrane Database of Systematic Reviews, Embase, and Google Scholar from inception to July 1, 2023.

STUDY SELECTION

In compliance with our PROSPERO registration (CRD42022347548), we selected articles comparing rSo2 measurements in adults either between racial groups or at different levels of skin pigmentation. Two independent reviewers conducted full-text reviews of all potentially relevant articles.

DATA EXTRACTION

We extracted data on self-reported race or level of skin pigmentation and mean rSo2 values.

DATA SYNTHESIS

Of the 11,495 unique records screened, two studies (n = 7,549) met our inclusion criteria for systematic review. Sun et al (2015) yielded significantly lower rSo2 values for African Americans compared with Caucasians, whereas Stannard et al (2021) found little difference between self-reported racial groups. This discrepancy is likely because Stannard et al (2021) used a NIRS platform which specifically purports to control for the effects of melanin. Several other studies that did not meet our inclusion criteria corroborated the notion that skin pigmentation results in lower rSo2 readings.

CONCLUSIONS

Skin pigmentation likely results in attenuated rSo2 readings. However, the magnitude of this effect may depend on the specific NIRS platform used.

Intraoperative application of regional cerebral oxygen saturation monitoring for geriatric patients in China: a survey

Background

Regional cerebral oxygen saturation (rSO2) monitoring is a real-time and non-invasive technique for estimating the balance of regional cerebral oxygen supply and consumption. Despite the growing popularity of this monitoring technique, data regarding outcome benefits remain sparse and contradictory. This study was conducted to explore the popularity and understanding of cerebral oxygen saturation monitoring during anesthesia in geriatric patients.

Methods

An online self-report questionnaire was distributed in March 2021 to various hospitals in China for dissemination to anesthesiologists. Questions surveyed cerebral oximetry equipment and utilization, demographics, and clinical practice of participants.

Results

In total, 447 anesthesiologists responded. Of these, 301 (67.3%) respondents reported that their hospitals were equipped with cerebral oximetry, which 274 anesthesiologists use during anesthesia. A high percentage of anesthesiologists chose to monitor rSO2 during cardiac surgery (77.4%, n = 212) and neurosurgery (40.5%, n = 111). Most anesthesiologists agreed that a 30% reduction from the rSO2 baseline requires intervention to avoid cerebral ischemia, mainly via elevating arterial pressure and fraction of inspired oxygen (FiO2). Of those without cerebral oximetry, 138 of 146 (94.5%) anesthesiologists were willing to monitor rSO2. In addition, 291 respondents believed that cerebral oxygen monitoring would help prevent postoperative cognitive dysfunction.

Conclusion

Our survey indicated that the prevalence of cerebral oximetry remains relatively low, while almost all anesthesiologists expressed their willingness to use rSO2 monitoring in geriatric anesthesia. Heterogeneity in clinical practice was identified, indicating relevant knowledge gaps that should encourage further clinical research to optimize treatment.

Challenges in Perioperative Cerebral Oximetry Monitoring: A Case of Clofazimine-Induced Skin Pigmentation Interference

Perioperative stroke is a potentially devastating complication in patients undergoing noncardiac surgery. The most consistent risk factor associated with the condition is a history of a prior stroke. Cerebral oximetry is a simple, non-invasive, and continuous monitoring device that uses near-infrared spectroscopy (NIRS) to monitor cerebral oxygenation. However, like other monitoring devices, cerebral oximetry has certain limitations, and it must be interpreted cautiously and by taking into account all available clinical information related to the patient. We present a case of a 62-year-old Caucasian woman with a past medical history of a transient ischemic attack (TIA), who had been advised to undergo a right pneumectomy by video-assisted thoracoscopic surgery for treating chronic infection of bronchiectasis. Before administering any drug and while the patient was still alert, we monitored NIRS, and the values recorded were 15 on the left side and 26 on the right side. Despite being Caucasian, she had a darker brownish skin color due to chronic clofazimine use, which is known to cause skin pigmentation. Skin pigmentation is known to attenuate the transmission of near-infrared (NIR) light, potentially affecting the estimation of cerebral oxygen saturation. Thus, our patient suffered from clofazimine-induced skin pigmentation, which may have interfered with the NIR light transmission, which explains the extremely low values observed. Regional intracerebral oxygen saturation should be interpreted in the context of all available clinical information since NIRS transmission can be influenced by several factors and skin pigment has been found to independently influence regional intracerebral oxygen saturation. Apart from race or high serum bilirubin concentration, we should also consider other causes of skin pigmentation alterations, such as pharmacological therapy.

Impact of Stepwise Recruitment Maneuvers on Cerebral Hemodynamics: Experimental Study in Neonatal Model

BACKGROUND

Lung recruitment maneuvers (LRMs) have been demonstrated to be effective in avoiding atelectasis during general anesthesia in the pediatric population. Performing these maneuvers is safe at the systemic hemodynamic and respiratory levels.

AIMS

We aimed to evaluate the impact of a stepwise LRM and individualized positive end-expiratory pressure (PEEP) on cerebral hemodynamics in an experimental neonatal model.

METHODS

Eleven newborn pigs (less than 72 h old, 2.56 ± 0.18 kg in weight) were included in the study. The LRM was performed under pressure-controlled ventilation with a constant driving pressure (15 cmH2O) in a stepwise increasing PEEP model. The target peak inspiratory pressure (PIP) was 30 cmH2O and the PEEP was 15 cmH2O. The following hemodynamic variables were monitored using the PICCO® system: mean arterial pressure (MAP), central venous pressure (CVP), and cardiac output (CO). The cerebral hemodynamics variables monitored were intracranial pressure (ICP) (with an intraparenchymal Camino® catheter) and cerebral oxygen saturation (rSO2) (with the oximetry monitor INVOS 5100® system). The following respiratory parameters were monitored: oxygen saturation, fraction of inspired oxygen, partial pressure of oxygen, end-tidal carbon dioxide pressure, Pmean, PEEP, static compliance (Cstat), and dynamic compliance (Cdyn).

RESULTS

All LRMs were safely performed as scheduled without any interruptions. Systemic hemodynamic stability was maintained during the lung recruitment maneuver. No changes in ICP occurred. We observed an improvement in rSO2 after the maneuver (+5.8%).

CONCLUSIONS

Stepwise LRMs are a safe tool to avoid atelectasis. We did not observe an impairment in cerebral hemodynamics but an improvement in cerebral oxygenation.

Monitoring the Cerebral Oximetry Index Along With In-line Cardiopulmonary Bypass Parameters in a High-Risk Patient Undergoing Cardiac Surgery: A Case Report

The quest to minimize the morbidity and mortality of patients undergoing cardiac surgery is ongoing. Impaired cerebral autoregulation and tissue malperfusion are linked with neurological complications. The cerebral oximetry index (COx) has been introduced as an index of cerebral autoregulation, while in-line monitoring enables the detection and prevention of metabolic disturbances during cardiopulmonary bypass (CPB). This report presents the case of a 58-year-old female patient scheduled for aortic valve replacement under minimally invasive extracorporeal circulation (MiECC). Her medical history consisted of epilepsy, multiple ischemic strokes, heavy smoking, and brachiocephalic artery stenosis. We sought to investigate the limits of autoregulation and the role of metabolic indices of perfusion on COx. Mean arterial blood pressure (ABP), cerebral oximetry (rSO₂), and in-line perfusion data during CPB were recorded at 10s intervals. The lower limit of autoregulation was 44mmHg on both sides and the upper limit was 98mmHg on the right and 107mmHg on the left side. A multiple linear regression analysis was performed to identify any potential predictors of COx values. Hemoglobin (Hb), PCO₂, flow, DO₂ index (DO₂i), Ο₂ extraction ratio (O₂ER), and perfusion ratio (PR) were included in the analysis. Significant equations were found on both sides. Predicted COx left was equal to 5.8 - 11.04O₂ER - 0.04Hb (p=0.001, R²= 0.15). Predicted COx right was equal to 3.06 - 0.3flow - 6.8O₂ER -0.03Hb + 0.02PCO₂ + 0.004DO₂i(p=0.03, R²=0.13). Targeting physiological perfusion and monitoring perfusion during CPB may have an additional impact on cerebral autoregulation and should be studied further.

Utility of cerebral oximetry in balloon mitral valvotomy and its correlation with post-procedure neurological complications: A pragmatic prospective observational study

Background and Aims

Neurological complications (NCs) are significantly associated with reduced regional cerebral saturation (rSO₂) in patients undergoing cardiac surgeries, as assessed with cerebral oximetry (COx). However, limited evidence is available in patients undergoing balloon mitral valvotomy (BMV). Thus, we evaluated the utility of COx in patients undergoing BMV, the incidence of BMV-related NCs and the association of >20% reduction in rSO₂ with NCs.

Methods

This pragmatic, prospective, observational study was performed after ethical approval, over November 2018 to August 2020, in the cardiology catherization laboratory of a tertiary care hospital. The study involved 100 adult patients undergoing BMV for symptomatic mitral stenosis. The patients were evaluated at initial presentation, pre-BMV, post-BMV and 3 months after the BMV.

Results

The incidence of NCs was 7%, including transient ischaemic attack (n = 3), slurred speech (n = 2) and hemiparesis (n = 2). A significantly greater proportion of patients with NCs had a > 20% decrease in the rSO₂ (P value = 0.020). At >20% cut-off, the COx had a sensitivity and specificity of 57.1% and 80%, respectively, in the prediction of NCs. Female sex (P value = 0.039), history of cerebrovascular episodes (P value < 0.001) and number of balloon attempts (P value < 0.001) were significantly associated with NCs. Patients with and without NCs had a significantly greater post-BMV mean % change in rSO₂ than pre-BMV (both right and left sides), but the magnitude of mean % change was greater in those with NCs.

Conclusions

COx alone has low sensitivity and specificity in the prediction of NCs and cannot reliably predict the development of post-BMV NCs.

Kinetics of tissue oxygenation index during fast and slow cardiopulmonary bypass initiation

INTRODUCTION

Despite being a daily clinical application in cardiac operating theaters, an evidence-based approach on how to optimally initiate the heart-lung machine (HLM) to prevent critical phases of cerebral ischemia is still lacking. We therefore designed a study comparing two different initiation times for starting the cardiopulmonary bypass (CPB).

METHODS

We conducted a monocentric, randomized, and prospective study comparing the impact of two initiation times, a rapid initiation of 15 s and a slow initiation of 180 s to reach the full target flow rate of 2.5 L/min/m² times the body surface area, on cerebral tissue oxygenation by near infrared spectroscopy measurements.

RESULTS

The absolute values in tissue oxygenation index (TOI) showed no difference between the groups before and after the CPB with a 10% drop in oxygenation index in both groups due to the hemodilution through the HLM priming. Looking at the kinetics a rapid initiation of CPB produced a higher negative rate of change in TOI with a total of 21% in critical oxygenation readings compared to 6% in the slow initiation group.

CONCLUSION

In order to avoid critical phases of cerebral ischemia during the initiation of CPB for cardiac procedures, we propose an initiation time of at least 90 s to reach the 100% of target flow rate of the HLM.

Impact of red blood cell transfusion on regional cerebral oxygen saturation during pediatric ECMO

BACKGROUND

Low cerebral regional tissue oxygenation (crSO2) is associated with unfavorable neurological outcomes in children requiring extracorporeal membrane oxygenation (ECMO) support. Red blood cell (RBC) transfusion can improve brain oxygenation and crSO2 has been proposed as a noninvasive monitoring tool that could aid in RBC transfusion decision-making. However, how crSO2 responds to RBC transfusion is largely unknown.

STUDY DESIGN AND METHODS

This was a retrospective, observational cohort study of all patients <21 years supported on ECMO at a single institution from 2011 to 2018. Transfusion events were grouped by pre-transfusion hemoglobin concentration (<10, 10- < 12, and ≥ 12 g/dL). Post- versus pre-transfusion crSO2 changes were analyzed using linear mixed-effects models.

RESULTS

The final cohort included 830 transfusion events in 111 patients. Hemoglobin increased significantly post- versus pre-RBC transfusion (estimated mean increase of 0.47 g/dL [95% CI, 0.35-0.58], p < .001), as did crSO2 (estimated mean increase of 1.82 percentage points [95% CI, 1.23-2.40], p < .001). Larger improvements in crSO2 were associated with lower pre-transfusion crSO2 values (p < .001). There was no difference in mean change in crSO2 across the three hemoglobin groups in unadjusted analysis (p = .5) or after adjusting for age, diagnostic category, and pre-transfusion rSO2 (p = .15). Pre-transfusion crSO2 was <50% for 112 of 830 (13.5%) transfusion events, with only 30 (26.8%) crSO2 measurements noted to increase ≥50% post-transfusion.

DISCUSSION

Among neonatal and pediatric patients on ECMO support, there was a statistically significant increase in crSO2 following RBC transfusion, although clinical significance needs to be investigated further. The effect was strongest among patients with lower crSO2 pre-transfusion.

Low Intraoperative Cerebral Oxygen Saturation Is Associated with Acute Kidney Injury after Off-Pump Coronary Artery Bypass

By monitoring the brain as the index organ of global oxygen supply-demand balance including major organs, regional cerebral oxygen saturation (rScO₂) may indicate adequacy of renal perfusion. The aim of this study was to investigate the relationship between perioperative rScO₂ and acute kidney injury (AKI) after off-pump coronary artery bypass (OPCAB). AKI was diagnosed according to the Kidney Disease: Improving Global Outcomes criteria. Collected rScO₂ variables were baseline, mean, and lowest value during surgery, maximal percentage decrease from baseline, and areas under the threshold below an absolute value of 50% (AUT₅₀) and of 80% of baseline (AUT_80%base). Among 580 patients, AKI developed in 143 (24.7%) patients. Patients with AKI had lower baseline, mean, and lowest rScO₂ and higher AUT₅₀ and AUT_80%base than those without AKI despite routine efforts to restore the rScO₂ values within 20% of the baseline. Among the rScO₂ variables, the area under the receiver operating characteristic curve of mean rScO₂ was the highest (0.636), which was used for the multivariable logistic regression. Multivariable logistic regression revealed mean rScO₂ as an independent predictor of AKI (odds ratio, 0.964; 95% confidence interval, 0.937-0.990; p = 0.008), along with chronic kidney disease and emergency surgery. Low intraoperative mean rScO₂ was independently associated with AKI after OPCAB, which may serve as an early marker of renal injury.

A comprehensive review of cerebral oximetry in cardiac surgery

BACKGROUND

Patients who undergo cardiac surgery are at increased risk of stroke, postoperative cognitive decline, and delirium. These neurocognitive complications have led to increased costs, intensive care unit stays, morbidity, and mortality. As a result, there is a significant push to mitigate any neurological complications in cardiac surgery patients. Near-infrared spectroscopy to measure regional cerebral oxygen saturations has gained consideration due to its noninvasive and user-friendly nature. Cerebral oximetry desaturations during cardiac surgery have been linked to an array of adverse clinical outcomes. However, the most effective intraoperative interventions to protect this vulnerable patient population have yet to be ascertained.

AIM OF STUDY

To provide a comprehensive summary of the intraoperative management for cerebral oximetry desaturations during cardiac surgery. The review highlights clinical outcomes from cerebral oximetry use to quantify the importance of identifying cerebral desaturations during cardiac surgery. The review then interrogates possible interventions for cerebral oximetry desaturations in an effort to determine which interventions are most efficacious and to enlighten possible areas for further research.

METHODS

A narrative review of randomized controlled trials, observational studies, and systematic reviews with metanalyses was performed through August 2021.

RESULTS

There is significant heterogeneity among patient populations for which cerebral oximetry monitoring has been studied in cardiac surgery. Further, the definition of a clinically significant cerebral desaturation and the assessment of neurocognitive outcomes varied substantially across studies. As a result, metanalysis is challenging and few conclusions can be drawn. Cerebral oximetry use during cardiac surgery has not been associated with improvements in neurocognitive outcomes, morbidity, or mortality to date. The evidence to support a particular intervention for an acute desaturation is equivocal.

CONCLUSIONS

Future research is needed to quantify a clinically significant cerebral desaturation and to determine which interventions for an acute desaturation effectively improve clinical outcomes.

The Influence of Age on Cerebral Tissue Oxygenation in Vasovagal Syncope and Orthostatic Hypotension

Age-related physiological impairment increases susceptibility to syncope. We tested the hypotheses that cerebral oxygenation during orthostatic provocation, as well as the level at which syncope occurs, differs according to age. Non-invasive hemodynamic monitoring and cerebral oximetry were applied during a head-up tilt test in 139 patients with vasovagal syncope (mean (SD) 45, (17) years, 60%-female); 121 patients with orthostatic hypotension (61.4 (19.2) years, 49.6%-female); and 82 patients with a negative head-up tilt test (45 (18) years, 61%-female). Group differences in cerebral tissue oxygenation levels and systolic blood pressure were assessed in supine at 3 and 10 min of orthostatic provocation, 30 s before (i.e., presyncopal phase) and during syncope in age groups of <30, 30−60, and >60 years. During the head-up tilt test, cerebral tissue oxygenation at the presyncopal phase decreased with age, both in patients with vasovagal syncope (<30 years: 66.9 ± 6.2, 30−60: 64.5 ± 6.1, >60: 62.2 ± 5.8%; p = 0.009) and orthostatic hypotension (<30: 67.4 ± 4.4, 30−60: 61.6 ± 6.2, >60: 57.5 ± 3.9; p < 0.001). Mean systolic blood pressure at the presyncopal phase did not differ according to age. Cerebral oxygenation prior to syncope in older individuals with vasovagal syncope and orthostatic hypotension is lower compared with younger individuals independently of systolic blood pressure. This suggests that the level of cerebral oxygenation at which syncope is elected is lower in older individuals.

Cerebral Tissue Oxygen Saturation Is Enhanced in Patients following Transcatheter Aortic Valve Implantation: A Retrospective Study

Transcatheter aortic valve implantation (TAVI) has emerged as an alternative to surgical aortic valve replacement. The aim of this study was to evaluate whether a relevant alteration in cerebral tissue oxygen saturation (rSO2) could be detected following TAVI. Retrospective data analysis included 275 patients undergoing TAVI between October 2016 and December 2020. Overall, rSO2 significantly increased following TAVI (64.6 ± 10% vs. 68.1 ± 10%, p < 0.01). However, a significant rise was only observed in patients with a preoperative rSO2 < 60%. Of the hemodynamic confounders studied, hemoglobin, mean arterial pressure and blood pH were lowered, while central venous pressure and arterial partial pressure of carbon dioxide (PaCO2) were slightly elevated (PaCO2: 39 (36−43) mmHg vs. 42 (37−47) mmHg, p = 0.03; pH: 7.41 (7.3−7.4) vs. 7.36 (7.3−7.4), p < 0.01). Multivariate linear regression modeling identified only hemoglobin as a predictor of altered rSO2. Patients with a EuroScore II above 4% and an extended ICU stay were found to have lower rSO2, while no difference was observed in patients with postoperative delirium or between the implanted valve types. Further prospective studies that eliminate differences in potential confounding variables are necessary to confirm the rise in rSO2. Future research should provide more information on the value of cerebral oximetry for identifying high-risk patients who will require further clinical interventions in the setting of the TAVI procedure.

Cerebral Oximetry-Monitored Nitroglycerin Infusion and Tissue Perfusion during Rewarming of Cardiopulmonary Bypass in Cardiac Surgery: A Prospective Randomized Trial

Background: Nitroglycerin facilitates microcirculation and oxygen delivery through vasodilation. The purpose of this study was to clarify the effects of nitroglycerin-induced vasodilation and potential hypotension on tissue perfusion under cerebral oximetry monitoring during rewarming in cardiopulmonary bypass. Methods: Elective cardiac surgical patients were randomly assigned to either a nitroglycerin group (n = 32) with an intravenous infusion of 1–5 mcg/kg/min or a control group (n = 31) with 0–0.1 mcg/kg/min infusion, since the initiation of rewarming. Perioperative arterial blood gas data were collected in addition to hemodynamic variables, cerebral oximetry values, urine output, and postoperative outcomes. Results: Nearly one-fifth (6/32) of patients in the nitroglycerin group experienced transient (≤5 min) profound hypotension (mean arterial blood pressure ≤40 mmHg) after the initiation of infusion. There were no significant differences between groups in terms of perioperative levels of cerebral oximetry, cardiac index, plasma glucose, lactate, bicarbonate, base excess, or post-bypass activated coagulation time. In the nitroglycerin group, urine output was nonsignificantly higher during cardiopulmonary bypass (p = 0.099) and within 8 h after surgery (p = 0.157). Perioperative transfused blood products, postoperative inotropic doses, extubation time, and intensive care unit stay were comparable for the two groups. Conclusions: Initiation of intravenous nitroglycerin infusion (at 1–5 mcg/kg/min) during rewarming in hypothermic cardiopulmonary bypass resulted in transient profound hypotension in one-fifth of patients and did not improve perioperative cerebral oxygenation, tissue perfusion, and coagulation in cardiac surgery.

The use of cerebral oximetry in cardiac surgery: A systematic review and meta-analysis of randomized controlled trials

High prevalence of cerebral desaturation is associated with postoperative neurological complications in cardiac surgery. However, the evidence use of cerebral oximetry by correcting cerebral desaturation in the reduction of postoperative complications remains uncertain in the literature. This systematic review and meta-analysis aimed to examine the effect of cerebral oximetry on the incidence of postoperative cognitive dysfunction in cardiac surgery. Databases of MEDLINE, EMBASE, and CENTRAL were searched from their inception until April 2021. All randomized controlled trials comparing cerebral oximetry and blinded/no cerebral oximetry in adult patients undergoing cardiac surgery were included. Observational studies, case series, and case reports were excluded. A total of 14 trials (n = 2,033) were included in this review. Our pooled data demonstrated that patients with cerebral oximetry were associated with a lower incidence of postoperative cognitive dysfunction than the control group (studies = 4, n = 609, odds ratio [OR]: 0.15, 95% confidence interval [CI]: 0.04 to 0.54, P = 0.003, I² = 88%; certainty of evidence = very low). In terms of postoperative delirium (OR: 0.75, 95%CI: 0.50-1.14, P = 0.18, I² = 0%; certainty of evidence = low) and postoperative stroke (OR: 0.81 95%CI: 0.37-1.80, P = 0.61, I² = 0%; certainty of evidence = high), no significant differences (P > 0.05) were reported between the cerebral oximetry and control groups. In this meta-analysis, the use of cerebral oximetry monitoring in cardiac surgery demonstrated a lower incidence of postoperative cognitive dysfunction. However, this finding must be interpreted with caution due to the low level of evidence, high degree of heterogeneity, lack of standardized cognitive assessments, and cerebral desaturation interventions.

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO₂ ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO₂ during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

The Use of Cerebral Oximetry in Surgery: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE

The evidence on the use of cerebral oximetry during surgery to minimize postoperative neurologic complications remains uncertain in the literature. The present authors aimed to assess the value of cerebral oximetry in the prevention of postoperative cognitive dysfunction, postoperative delirium, and postoperative stroke in adults undergoing surgery.

DESIGN

A systematic review and meta-analysis.

SETTING

The surgery room.

PARTICIPANTS

Adult patients (ages ≥18 years) undergoing surgery.

INTERVENTIONS

Cerebral oximetry monitoring.

MEASUREMENTS AND MAIN RESULTS

Databases of Ovid MEDLINE, Ovid EMBASE, and CENTRAL were systematically searched from their inception until December 2020 for randomized controlled trials comparing cerebral oximetry monitoring with either blinded or no cerebral oximetry monitoring in adults undergoing surgery. Observational studies, case reports, and case series were excluded. Seventeen studies (n = 2,120 patients) were included for quantitative meta-analysis. Patients who were randomized to cerebral oximetry monitoring had a lower incidence of postoperative cognitive dysfunction (studies = seven, n = 969, odds ratio [OR] 0.23, 95% confidence interval [CI] 0.11-0.48, p = 0.0001; evidence = very low). However, no significant differences were observed in the incidence of postoperative delirium (studies = five, n = 716, OR 0.81, 95% CI 0.53-1.25, p = 0.35; evidence = high), and postoperative stroke (studies = seven, n = 1,087, OR 0.72, 95% CI 0.30-1.69, p = 0.45; evidence = moderate).

CONCLUSION

Adult patients with cerebral oximetry monitoring were associated with a significant reduction of postoperative cognitive dysfunction. However, given the low certainty of evidence and substantial heterogeneity, more randomized controlled trials using standardized assessment tools for postoperative cognitive dysfunction and interventions of correcting cerebral desaturation are warranted to improve the certainty of evidence and homogeneity.

Cerebral oximetry monitoring in non-intubated patients undergoing endoscopic retrograde cholangiopancreatography under propofol-induced sedation: a prospective observational study

Background

Prolonged propofol-induced deep sedation increases the risk for sedation-related complications. Cerebral oximetry enables prompt assessment of tissue oxygenation by demonstrating the regional hemoglobin oxygen saturation (rSO₂) of the cerebral cortex. This study aimed to: evaluate cerebral oxygenation under deep sedation during an endoscopic retrograde cholangiopancreatography (ERCP) procedure; determine the cerebral desaturation event (CDE) rate; and assess the predictive capacity of CDEs for sedation-related complications.

Methods

All consecutive patients who underwent ERCP between September and December 2019 were included prospectively. Propofol monotherapy was used and sedation level was assessed using the bispectral index (BIS). The target level of sedation was deep sedation, defined by BIS values 40-60. Participants were monitored with arterial blood gas analysis and INVOS 5100C cerebral oximeter. RSO₂ values were registered prior to sedation (baseline value), every 5 min during the sedation period and at recovery of consciousness. BIS values were recorded simultaneously. CDE was defined as a drop >10% from individual baseline rSO₂.

Results

Sixty patients were enrolled. Mean baseline rSO₂ was 65.1% and BIS values ranged from 18-85. No significant correlation was observed between mean rSO₂ measurements and mean BIS values throughout the recordings (P = 0.193). Data from patients aged ≥65 years were analyzed separately and the results were similar. The CDE rate was 2.7%, but no CDE was associated with clinical manifestations. Twelve sedation-related complications occurred without the presence of cerebral desaturation.

Conclusion

Cerebral oxygenation remained independent of changes in sedation depth and cerebral oximetry monitoring did not detect complications earlier than standard monitors.

Outcomes in Cardiac Surgery Based on Preoperative, Mean Intraoperative and Stratified Cerebral Oximetry Values

INTRODUCTION

Cardiac surgery is associated with significant morbidity and longer length-of-stay (LOS) than most other surgeries. Regional cerebral oximetry (rSO2) using near-infrared spectroscopy (NIRS) on the patient's forehead monitors cerebral oxygenation during surgery and cardiopulmonary bypass (CPB). Its purpose is to detect and manage periods of cerebral hypoxia which may otherwise go undetected, thereby reducing morbidity. But outcomes have been inconsistent, and not all cardiac departments have adopted this non-invasive, simple-to-use technology. We aimed to study the efficacy of our use of rSO2 by recording seven outcomes for each patient according to their preoperative rSO2, the mean intraoperative rSO2, and four ischemic thresholds during surgery.

METHOD

This is a retrospective audit of cardiac surgical patients in whom a protocol was used to maintain rSO2 above the preoperative value and studied seven major morbidity outcomes. Cerebral oximetry data were recorded for each patient and analyzed for six variables: preoperative baseline rSO2, mean intraoperative rSO2, and four ischemic thresholds defined as an area under the curve (AUC) in minutes% below the baseline rSO2,minus 10% below the baseline, minus 20% the below baselineand minus 50% below baseline. Outcomes examined were: delirium, stroke, postoperative rise in creatinine of 50 mmol, absolute creatinine of 200 mmol, need for new renal replacement therapy (RRT), hospital LOS and inpatient mortality.

RESULTS

Complete data were available for 166 patients. Lower mean preoperative rSO2 was associated with stroke (p=0.031), mild and severe renal dysfunction (p=0.045 and p=0.036), death-in-hospital (p=0.027) and prolonged hospital LOS (p=0.005). Lower mean intraoperative rSO2 during surgery was associated with the outcomes of renal dysfunction, mild (p=0.027), moderate (p=0.003) or severe (p=0.002), death-in-hospital (p=0.003) and prolonged hospital LOS (p=0.015). Of the four ischemic thresholds defined, only new RRT occurring at minus 20% and minus 50% below baseline was significant.

CONCLUSION

Lower preoperative rSO2 and mean intraoperative rSO2 were associated with poor outcomes, notably leading to a significant increase in hospital LOS. Mild degrees of cerebral ischemia below the baseline and minus 10% of the baseline during surgery were well tolerated.

Cerebral Oximetry during Out-of-Hospital Resuscitation: Pilot Study of First Responder Implementation

Background: Anoxic brain injury is a common mode of death following out-of-hospital cardiac arrest (OHCA). We assessed the course of regional cerebral oxygen saturation (rSO₂) at the outset and during first responder resuscitation to understand its relationship with return of spontaneous circulation (ROSC) and functional survival. Methods: We undertook a prospective observational investigation of adult OHCA patients treated by a first-responder EMS agency in King County, WA. Cerebral oximetry was performed using the SenSmart® Model X-100 Universal Oximetry System (Nonin Medical, Inc). We determined cerebral oximetry rSO₂ overall and stratified according to ROSC and favorable survival status defined by Cerebral Performance Category (CPC) of 1-2. Results: Among the 59 OHCA cases enrolled, 47% (n = 28) achieved ROSC and 14% (n = 8) survived with CPC 1-2. On average, initial rSO₂ cerebral oximetry was 41% and was not different at the outset according to return of spontaneous circulation (ROSC) or survival status. Within 5 minutes of first responder resuscitation, those who would subsequently achieve ROSC had a higher rSO₂ than those who would not achieve ROSC (51% vs. 43%, p = 0.03). Among patients who achieved ROSC, those who would survive with CPC 1-2 had a higher rSO₂ cerebral oximetry following ROSC than nonsurvivors (74% vs. 60%, p = 0.04 at 5 minutes post ROSC), a difference that was not evident in the minutes prior to ROSC (55% vs. 51% at 3 minutes prior to ROSC, p = 0.5). Conclusion: In this observational study, where first responders applied cerebral oximetry, higher rSO₂ during the course of care predicted ROSC among all patients and predicted favorable survival among those who achieved ROSC. Future investigation should evaluate whether and how treatments might modify rSO₂ and in turn may influence prognosis.

Near-Infrared Spectroscopy (NIRS) for Cerebral and Tissue Oximetry: Analysis of Evolving Applications

THE USE OF NEAR-INFRARED SPECTROSCOPY (NIRS) has increased significantly worldwide in the past decade. This technology, first described more than 40 years ago, is based on the fact that near-infrared light is able to penetrate biologic tissue and can obtain real-time, noninvasive information on tissue oxygenation and metabolism. In the clinical setting, NIRS has been able to provide clinicians potentially valuable information in patients with impaired microcirculations (systemic and cerebral). Near-infrared spectroscopy has progressed beyond assessment of brain oxygenation to monitor local tissue and muscle oxygenation and perfusion. This review analyzes the published data and provides the clinician a comprehensive account of the perioperative utility of NIRS in cardiac, vascular and thoracic surgery, as well as its increasing role in tissue/muscle oxygenation monitoring.

Usefulness of Cerebral Oximetry in TBI by NIRS

Measurement of cerebral oximetry by near-infrared spectroscopy provides continuous and non-invasive information about the oxygen saturation of haemoglobin in the central nervous system. This is especially important in the case of patients with traumatic brain injuries. Monitoring of cerebral oximetry in these patients could allow for the diagnosis of inadequate cerebral oxygenation caused by disturbances in cerebral blood flow. It could enable identification of episodes of hypoxia and cerebral ischemia. Continuous bedside measurement could facilitate the rapid diagnosis of intracranial bleeding or cerebrovascular autoregulation disorders and accelerate the implementation of treatment. However, it should be remembered that the method of monitoring cerebral oximetry by means of near-infrared spectroscopy also has its numerous limitations, resulting mainly from its physical properties. This paper summarizes the usefulness of monitoring cerebral oximetry by near-infrared spectroscopy in patients with traumatic brain injury, taking into account the advantages and the disadvantages of this technique.

Surgical treatment in symptomatic stenosis of the carotid artery and persistent primitive hypoglossal artery

Persistent primitive hypoglossal artery is a rare variant of intrauterine anastomosis between the carotid and basilar arteries, which may remain in adults. The presence of this artery in carotid artery atherosclerosis increases the risks for stroke in the carotid and basilar basins. Our clinical case illustrates successful carotid endarterectomy in the presence of an ipsilateral persistent primitive hypoglossal artery under cerebral oximetry control.

The Regional Cerebral Oxygen Saturation Effect of Inotropes/Vasopressors Administered to Treat Intraoperative Hypotension: A Bayesian Network Meta-analysis

One of the main concerns of intraoperative hypotension is adequacy of cerebral perfusion, as cerebral blood flow decreases passively when mean arterial pressure falls below the lower limit of cerebral autoregulation. Treatment of intraoperative hypotension includes administration of drugs, such as inotropes and vasopressors, which have different pharmacological effects on cerebral hemodynamics; there is no consensus on the preferred drug to use. We performed a network meta-analysis (NMA) to pool and analyze data comparing the effect on cerebral oxygen saturation (ScO 2 ) measured by cerebral oximetry of various inotropes/vasopressors used to treat intraoperative hypotension. We searched randomized control trials in Embase, Ovid Medline, Scopus, Cochrane Central Register of Controlled Trials, and Web of Science. We included studies that enrolled adult patients undergoing surgery under general/spinal anesthesia that compared at least 2 inotropes/vasopressors to treat hypotension. We reviewed 51 full-text manuscripts and included 9 randomized controlled trials in our study. The primary outcome was change in ScO 2 . Our results showed the likelihood that dopamine, ephedrine, and norepinephrine had the lowest probability of decreasing ScO 2 . The suggested rank order to maintain ScO 2 , from higher to lower, was dopamine <ephedrine <norepinephrine <phenylephrine. Drugs in the lower rank order, like phenylephrine, produce higher reductions in ScO 2 . Compared with dopamine, the mean difference (95% credible interval) of ScO 2 reduction was: ephedrine -3.19 (-15.74, 8.82), norepinephrine -4.44 (-18.23, 9.63) and phenylephrine -6.93 (-18.31, 4.47). The results of our NMA suggest that dopamine and ephedrine are more likely to preserve ScO 2 , followed by norepinephrine. Compared with the other inotropes/vasopressors, phenylephrine decreased ScO 2 . Because of the inherent imprecision of direct/indirect comparisons, the rank orders are possibilities, not absolute ranks. Therefore the results of this NMA should be interpreted with caution.

The Year in Review: Anesthesia for Congenital Heart Disease 2020

This review focuses on the literature published during the calendar year 2020 that is of interest to anesthesiologists taking care of children and adults with congenital heart disease. Five major themes are discussed, including COVID-19 in children with heart disease, race and outcome disparities in congenital heart disease, Norwood procedure and outcomes, Fontan procedure and outcomes, and neurotoxicity/neurologic outcomes. A total of 59 peer-reviewed articles are discussed.

Cerebral Perfusion in Hemodialysis Patients: A Feasibility Study

Background

Patients on hemodialysis (HD) are known to exhibit low values of regional cerebral oxygenation (rSO2) and impaired cognitive functioning. The etiology of both is currently unknown.

Objective

To determine the feasibility of serially monitoring rSO2 in patients initiating HD. In addition, we sought to investigate how rSO2 is related to hemodynamic and dialysis parameters.

Design

Prospective observational study.

Setting

Single-center tertiary academic teaching hospital in Ontario, Canada.

Participants

Six patients initiating HD were enrolled in the study.

Methods

Feasibility was defined as successful study enrollment (>1 patient/month), successful consent rate (>70%), high data capture rates (>90%), and assessment tolerability. Regional cerebral oxygenation monitoring was performed 1 time/wk for the first year of dialysis. A neuropsychological battery was performed 3 times during the study: before dialysis initiation, 3 months, and 1 year after dialysis initiation. The neuropsychological battery included a traditional screening tool: the Repeatable Battery for the Assessment of Neuropsychological Status, and a robot-based assessment: Kinarm.

Results

Our overall consent rate was 33%, and our enrollment rate was 0.4 patients/mo. In total 243 rSO2 sessions were recorded, with a data capture rate of 91.4% (222/243) across the 6 patients. Throughout the study, no adverse interactions were reported. Correlations between rSO2 with hemodynamic and dialysis parameters showed individual patient variability. However, at the individual level, all patients demonstrated positive correlations between mean arterial pressure and rSO2. Patients who had more than 3 liters of fluid showed significant negative correlations with rSO2. Less cognitive impairment was detected after initiating dialysis.

Limitation

This small cohort limits conclusions that can be made between rSO2 and hemodynamic and dialysis parameters.

Conclusions

Prospectively monitoring rSO2 in patients was unfeasible in a single dialysis unit, due to low consent and enrollment rates. However, rSO2 monitoring may provide unique insights into the effects of HD on cerebral oxygenation that should be further investigated.

Trial Registration

Due to the feasibility nature of this study, no trial registration was performed.

Effects of a dual-filter-based cerebral embolic protection device in transcatheter aortic valve replacement on cerebral oxygen saturation: A prospective pilot study

PURPOSE

The Sentinel Cerebral Protection System (Sentinel-CPS) is increasingly used in transcatheter aortic valve replacement (TAVR). However, the impact of inserting the Sentinel-CPS inside the brain-supplying arteries on cerebral perfusion and oxygenation is unknown.

METHODS

Twenty patients undergoing transfemoral TAVR with (n = 10) and without (n = 10) cerebral embolic protection using the Sentinel-CPS were prospectively observed. All patients received conscious sedation and cerebral oxygen saturation (rSO₂ ) was continuously measured with near-infrared spectroscopy (NIRS). The cumulative perioperative cerebral desaturation was calculated for each patient by multiplying rSO₂ below an individualized desaturation threshold by time. In addition, rSO₂ values at the time of Sentinel-CPS insertion, filter positioning, and device retraction were analyzed.

RESULTS

There was no significant difference in cumulative cerebral desaturation in patients with Sentinel-CPS (median [IQR]) (0 [0/81] s%) and without (median [IQR]) (0 [0/23] s%), p = .762. A total of 6 patients (33.3%) experienced a perioperative decrease in rSO₂ below the individualized desaturation threshold (n = 3 with Sentinel-CPS, n = 3 without Sentinel-CPS; p = 1.000). Cerebral desaturation was detected during valve deployment (n = 5) and after postdilatation (n = 1). No desaturation events occurred during Sentinel-CPS insertion, filter positioning, or retraction.

CONCLUSION

Our pilot study revealed no difference in cumulative perioperative cerebral desaturation between TAVR with and without Sentinel-CPS. Catheter- and filter-based manipulations in the brain-supplying arteries for Sentinel-CPS application were not associated with a decrease of cerebral perfusion and oxygenation.

Cerebral Oxygenation and Autoregulation in Preterm Infants (Early NIRS Study)

OBJECTIVE

To determine if decreased cerebral oxygenation or altered cerebral autoregulation as measured by near-infrared spectroscopy (NIRS) in the first 96 postnatal hours is associated with an increased risk of death or severe neuroradiographic abnormalities in very preterm infants.

STUDY DESIGN

The Early NIRS prospective, multicenter study enrolled very preterm infants with a birth weight of <1250 g from 6 tertiary neonatal intensive care units. Mean arterial blood pressure and cerebral oxygen saturation (Csat) were continuously monitored using a neonatal sensor until 96 hours of age. Moving window correlations between Csat and mean arterial blood pressure determined time periods with altered cerebral autoregulation, and percentiles of correlation were compared between infants with and without the adverse outcome of mortality or severe neuroradiographic abnormalities by early cranial ultrasound.

RESULTS

Of 103 subjects with mean gestational age of 26 weeks, 21 (20%) died or had severe neuroradiographic abnormalities. Infants with adverse outcomes had a lower mean Csat (67 ± 9%) compared with those without adverse outcomes (72 ± 7%; P = .02). A Csat of <50% was identified as a cut-point for identifying infants with adverse outcome (area under the curve, 0.76). Infants with adverse outcomes were more likely to have significant positive or negative correlations between Csat and mean arterial blood pressure, indicating impaired cerebral autoregulation (P = .006).

CONCLUSIONS

Early NIRS monitoring may detect periods of lower cerebral oxygenation and altered cerebral autoregulation, identifying preterm infants at risk for mortality or neuroradiographic injury. An improved understanding of the relationship between altered hemodynamics and cerebral oxygenation may inform future strategies to prevent brain injury.

Validation of a Novel NeurOs Cerebral Oximetry Monitor Against the INVOS Monitor During Cardiac Surgery

OBJECTIVES

To compare the performance of a novel NeurOs cerebral oximetry monitor against the INVOS monitor during the entire intraoperative phase of cardiac surgery, including periods of known fluctuation in brain oxygenation, such as preoxygenation, induction, cannulation, and cardiopulmonary bypass.

DESIGN

This study was a prospective, nonrandomized, healthcare-provider and outcome-assessor blinded study.

SETTING

Tertiary care university hospital; single institutional study.

PARTICIPANTS

Twenty-three patients who underwent cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Both self-adhesive INVOS sensors and the assembled NeurOs sensors were placed accordingly when the patient arrived in the operating room.

MEASUREMENTS AND MAIN RESULTS

Ten out of 13 cases under the normal mode and eight out of the 10 cases under the high- sensitivity mode showed significant correlations between the NeurOs and INVOS groups (p < 0.05, r value from 0.24-0.88). When all cases were combined, NeurOs demonstrated significant correlation with INVOS (r = 0.5, 95% confidence interval [CI] 0.44-0.56, p < 0.01 for normal mode; r = 0.69, 95% CI 0.64 to 0.74, p < 0.01 for high-sensitivity mode) in both modes. To evaluate the data diversity, the authors performed a cluster analysis and found much less variation existed in the NeurOs normal mode when compared with INVOS (standard deviation [SD] 16.6% in INVOS, 4% in NeurOs normal mode) but similar patterns in the high-sensitivity mode (SD 17.6% in INVOS, 15.2% in NeurOs high-sensitivity mode). Bland-Altman plot analysis showed that most of the data fell between ± 1.96 SD lines, which demonstrated good consistency between these two methods under both modes of NeurOs (-28.8 to 30.8 in the normal mode; -36.6 to 32.7 in high-sensitivity mode). In the normal mode of NeurOs monitoring, receiver operating characteristic analysis suggested a 2% cutoff point was most optimal from the baseline for detecting hyperoxia (sensitivity 73%; specificity 66%) and minus 1% (sensitivity 66%; specificity 67%) for detecting hypoxia. Whereas in the high-sensitivity mode, the optimal cutoff point was 3% from baseline for detecting hyperoxia (sensitivity 75%; specificity 68%), and minus 3% for detecting hypoxia (sensitivity 90%; specificity 45%).

CONCLUSIONS

In conclusion, the novel NeurOs system was found to correlate with INVOS cerebral oximetry measurements during cardiac surgery.

Cerebral Oximetry Monitoring in Patients Undergoing Surgery for Stanford Type A Aortic Dissection

OBJECTIVES

The aim of this study was to evaluate the prognostic impact of cerebral regional oxygen saturation (crSO₂) in patients undergoing surgery for Stanford type A aortic dissection (TAAD).

DESIGN

Observational, retrospective, institutional study.

SETTING

University hospital.

PARTICIPANTS

A total of 152 patients who underwent surgery for TAAD from June 2009 to December 2018 at the authors' institution.

INTERVENTIONS

Surgery for TAAD using continuous perioperative monitoring of crSO₂ with near-infrared cerebral oximetry (INVOS, Medtronic, MN).

MEASUREMENTS AND RESULTS

The rates of postoperative stroke/global brain ischemia were 22.4% and of hospital mortality 14.5%. Age, hemoglobin, and cardiogenic shock were independent predictors of nadir crSO₂ from both frontal areas at arrival to the operating room. Repeated measures test showed that changes in crSO₂ between the first measurement at operating room arrival, at the start of surgery, and at the end of surgery were not significant when measured on the right frontal area (p = 0.632), left frontal area (p = 0.608), as a nadir value from both frontal areas (p = 0.690), and as a difference between frontal areas (p = 0.826) in patients with and without major neurologic complications. Patients who had a nadir crSO₂ <40% anytime during the perioperative period, had a numerically higher rate of major neurologic complications (27.3% v 20.4%, p = 0.354), but this difference did not reach statistical significance. The incidence of nadir of crSO₂ value <40% at operating room arrival (5.9%, p = 1.000), at the start of surgery (5.3%, p = 0.685), and at the end of surgery (1.3%, p = 1.000) was rather low and not associated with these adverse events.

CONCLUSIONS

Derangements in crSO₂ detected by cerebral oximetry before and during surgery for TAAD did not predict postoperative stroke and/or global brain ischemia.

The Association of Cerebral Desaturation During One-Lung Ventilation and Postoperative Recovery: A Prospective Observational Cohort Study

OBJECTIVES

This study was designed to investigate whether cerebral oxygen desaturations during thoracic surgery are predictive of patients' quality of recovery. As a secondary aim, the authors investigated the relationship among cerebral desaturations and postoperative delirium and hospital length of stay.

DESIGN

This study was a prospective observational cohort study.

SETTING

A single tertiary-care medical center from September 2012 through March 2014.

PATIENTS

Adult patients scheduled for elective pulmonary surgery requiring one-lung ventilation.

INTERVENTIONS

All patients were monitored with the ForeSight cerebral oximeter.

MEASUREMENTS AND MAIN RESULTS

The primary assessment tool was the Postoperative Quality of Recovery Scale. Delirium was assessed using the Confusion Assessment Method. Of the 117 patients analyzed in the study, 60 of the patients desaturated below a cerebral oximetry level of 65% for a minimum of 3 minutes (51.3%). Patients who desaturated were significantly less likely to have cognitive recovery in the immediate postoperative period (p = 0.012), which did not persist in the postoperative period beyond day 0. Patients who desaturated also were more likely to have delirium (p = 0.048, odds ratio 2.81 [95% CI 1.01-7.79]) and longer length of stay (relative duration 1.35, 95% CI 1.05-1.73; p = 0.020).

CONCLUSIONS

Intraoperative cerebral oxygen desaturations, frequent during one-lung ventilation, are associated significantly with worse early cognitive recovery, high risk of postoperative delirium, and prolonged length of stay. Large interventional studies on cerebral oximetry in the thoracic operating room are warranted.

Impact of hypotension on cerebral perfusion during general anesthesia induction: A prospective observational study in adults

INTRODUCTION

During anesthesia, decreases in mean arterial pressure (MAP) are common but the impact on possible cerebral hypoperfusion remains a matter of debate. We evaluated cerebral perfusion in patients with or without cardiovascular comorbidities (Hi-risk vs Lo-risk) during induction of general anesthesia and during hypotensive episodes.

METHODS

Patients scheduled for neuroradiology procedure using standardized target-controlled Propofol-Remifentanil infusion were prospectively included. Monitoring included Transcranial Doppler (TCD) measuring mean blood velocity of the middle cerebral artery (Vm), Bispectral Index with burst suppression ratio (SR) and cerebral Near-Infrared Spectroscopy (NIRS). Hypotensive episodes were treated with a 10 µg bolus of Norepinephrine.

RESULTS

Eighty-one patients were included, 37 Hi-risk and 44 Lo-risk. During induction of anesthesia, MAP and Vm decreased in all patients, with greater changes observed in Hi-risk patients compared to Lo-risk patients (-34 [38-29]% vs -17 [25-8]%, P < .001 and -39 [45-29]% vs -28 [34-19]%, P < .01 respectively). In Hi-risk patients, the MAP-decrease correlated with the Vm-decrease (r = .48, P < .01), and was associated with more frequent occurrences of SR (21 vs 5 patients, P < .01 for Hi-risk vs Lo-risk). For the MAP-increase induced by norepinephrine, the Vm-increase was greater in Hi-risk than in Lo-risk patients (+15 [8-21]% vs +4 [1-11]%, P < .01). During induction and norepinephrine boluses, NIRS values did not follow acute changes of Vm.

CONCLUSION

Our results showed that Hi-risk patients had a higher decrease in MAP and Vm, and a higher occurrence of SR during induction of anesthesia than Lo-risk patients. Correction of MAP with norepinephrine increased Vm mainly in Hi-rik patients.

Changes in cerebral oxygenation and cerebral blood flow during hemodialysis - A simultaneous near-infrared spectroscopy and positron emission tomography study

Near-infrared spectroscopy (NIRS) is used to monitor cerebral tissue oxygenation (rSO₂) depending on cerebral blood flow (CBF), cerebral blood volume and blood oxygen content. We explored whether NIRS might be a more easy applicable proxy to [¹⁵O]H₂O positron emission tomography (PET) for detecting CBF changes during hemodialysis. Furthermore, we compared potential determinants of rSO₂ and CBF. In 12 patients aged ≥ 65 years, NIRS and PET were performed simultaneously: before (T1), early after start (T2), and at the end of hemodialysis (T3). Between T1 and T3, the relative change in frontal rSO₂ (ΔrSO₂) was -8 ± 9% (P = 0.001) and -5 ± 11% (P = 0.08), whereas the relative change in frontal gray matter CBF (ΔCBF) was -11 ± 18% (P = 0.009) and -12 ± 16% (P = 0.007) for the left and right hemisphere, respectively. ΔrSO₂ and ΔCBF were weakly correlated for the left (ρ 0.31, P = 0.4), and moderately correlated for the right (ρ 0.69, P = 0.03) hemisphere. The Bland-Altman plot suggested underestimation of ΔCBF by NIRS. Divergent associations of pH, pCO₂ and arterial oxygen content with rSO₂ were found compared to corresponding associations with CBF. In conclusion, NIRS could be a proxy to PET to detect intradialytic CBF changes, although NIRS and PET capture different physiological parameters of the brain.

Near-Infrared-Based Cerebral Oximetry for Prediction of Severe Acute Kidney Injury in Critically Ill Children After Cardiac Surgery

Supplemental Digital Content is available in the text.

Cerebral oximetry by near-infrared spectroscopy is used frequently in critically ill children but guidelines on its use for decision making in the PICU are lacking. We investigated cerebral near-infrared spectroscopy oximetry in its ability to predict severe acute kidney injury after pediatric cardiac surgery and assessed its additional predictive value to routinely collected data.

Dysfunctional cerebral autoregulation is associated with delirium in critically ill adults

Delirium is common during critical illness and is associated with morbidity and mortality, but its pathophysiology is unknown. We tested whether dysfunctional cerebral autoregulation (CA) contributes to the development of delirium. Adult patients (n = 40) with respiratory failure and/or shock were prospectively enrolled. Continuous recordings of regional cerebral oxygen saturation (rSO₂) were obtained by near-infrared spectroscopy (NIRS) during the first 72 h of intensive care unit (ICU) admission. CA function was estimated by the cerebral oximetry index (COx), which is the time-varying correlation between rSO₂ and mean arterial pressure (MAP). Delirium was assessed daily. The median ICU stay was seven days (IQR 4-13). Twenty-four patients (60%) screened positive for delirium on at least one day during their stay. Taking positive COx values to reflect periods of CA dysfunction, we found that the cumulative duration of CA dysfunction during the first one to three days in the ICU was significantly associated with the subsequent development of delirium. Additionally, we assessed two alternative methods for estimating optimal MAP targets in individual patients. In summary, early disturbances in CA may contribute to delirium, and NIRS-derived rSO2 may be used to identify individual perfusion targets in critically ill patients.

Combined Monitoring-Brain Function Monitoring and Cerebral Oximetry

Peri-operative brain function monitoring is still seen by most clinicians as complex, difficult to interpret and is therefore adopted very slowly. Current available technology mainly focusses on either a processed parameter based on the electroencephalogram to titrate anesthetics and central acting agents or on cerebral oximetry, a wider term to obtain information on the cerebral oxygen balance. There is still a lack of technological offerings that allow to monitor both entities in one device. However, there is scientific evidence that it is possible to combine measurements in an algorithmic approach that allows to better manage brain function in the surgical setting. Such integrated solutions should be made available to clinicians as they are likely to optimize patient care dependent on a sound health technology assessment.

Inadequacy of near-infrared spectroscopy cerebral oximetry monitoring for detecting neurological complication

Near-infrared spectroscopy (NIRS) cerebral oximetry is an established and standard monitoring modality for surgery under extracorporeal circulation with circulatory arrest. It helps to reduce the neurological complication, but in many instances, it becomes not only technically challenging but also is difficult to interpret and take corrective action based on the NIRS values. In this case study, we aimed to present the inadequacy of cerebral oximetry for detecting neurological complication.

Approaches for calibration and validation of near-infrared optical methods for oxygenation monitoring

Pulse oximetry for arterial oxygenation monitoring and tissue oximetry for monitoring of cerebral oxygenation or muscle oxygenation are based on quantitative in vivo diffuse optical spectroscopy. However, in both cases the information on absolute or relative concentration of human tissue constituents and especially on hemoglobin oxygenation can often not be retrieved by model-based analysis. An in vivo calibration against an accepted reference measurement can be a practical alternative. Pulse oximeters and most of commercial cerebral tissue oximeters rely on empirical calibration based on invasive controlled human desaturation studies. As invasive in vivo tests on healthy subjects are ethically disputable and should be limited to exceptional cases this calibration practice is unsatisfactory. We present the current status and problems of calibration and validation in pulse oximetry and cerebral tissue oximetry including the pros and cons of in vivo as well as in vitro methods. We emphasize various digital and physical phantom approaches and discuss the prospects of their application and possible further developments.

Cerebral Oxygen Saturation and Negative Postoperative Behavioral Changes in Pediatric Surgery: A Prospective Observational Study

OBJECTIVE

To evaluate if an intraoperative cerebral regional oxygen saturation (crSO₂) decrease, less pronounced than 20% below baseline (the current threshold believed to be associated with cognitive dysfunction in adults), is associated with negative postoperative behavioral changes (NPOBC) in the pediatric population after noncardiac surgeries.

STUDY DESIGN

A prospective observational study was conducted with 198 children aged 2-12 years old scheduled for noncardiac procedures under general anesthesia. Intraoperatively, crSO₂ was monitored with a cerebral oximeter. On postoperative day 7, the Post-Hospital Behavior Questionnaire was used to diagnose NPOBC.

RESULTS

The incidence of NPOBC was 38.8%. Logistic regression analysis revealed that with every 1% reduction of crSO₂ from the baseline value, the odds of developing NPOBC were 1.199 higher. Likewise, preoperative anxiety (OR 2.832, P = .006), duration of surgery (OR 1.026, P < .0001), and being between the ages of 2 and 3 years (OR 2.604, P = .048) were associated with NPOBC incidence. The multivariable logistic regression model receiver operating characteristic curve showed an area under the curve (95% CI) = 0.820 (0.759-0.881).

CONCLUSIONS

During noncardiac surgeries in the pediatric population, an intraoperative decrease in crSO₂ less pronounced than 20% from the baseline value is associated with negative postoperative behavior changes on postoperative day 7. The long-term implications remain to be determined, but this supports attention to crSO₂ during noncardiac surgeries.

Postoperative cerebral oximetry monitoring helps in early detection of diminished flow in Blalock-Taussig shunt

Cerebral oximeter is a noninvasive device which provides continuous monitoring of the regional cerebral saturation using near-infrared spectroscopy (NIRS). After gaining popularity as an intraoperative monitoring tool, use of NIRS monitoring has also expanded to postoperative period of congenital heart diseases now. Shunt underflow is a known complication after Blalock–Taussig (BT) shunt, which is conventionally detected by a drop in oxygen saturation and metabolic acidosis. We report a case where cerebral regional saturation monitoring by NIRS helped in early detection of low pulmonary flow state during postoperative period of neonatal BT shunt. We observed that the drop in regional cerebral oxygen saturation preceded fall in peripheral oxygen saturation during shunt underflow.

Regional Cerebral Oximetry as an Indicator of Acute Brain Injury in Adults Undergoing Veno-Arterial Extracorporeal Membrane Oxygenation-A Prospective Pilot Study

Background: Regional cerebral oxygen saturation (rScO2) measured by near-infrared spectroscopy (NIRS) can be used to monitor brain oxygenation in extracorporeal membrane oxygenation (ECMO). ECMO patients that develop acute brain injuries (ABIs) are observed to have worse outcomes. We evaluated the association between rScO2 and ABI in venoarterial (VA) ECMO patients. Methods: We retrospectively reviewed prospectively-collected NIRS data from patients undergoing VA ECMO from April 2016 to October 2016. Baseline demographics, ECMO and clinical characteristics, cerebral oximetry data, neuroradiographic images, and functional outcomes were reviewed for each patient. rScO2 desaturations were defined as a >25% decline from baseline or an absolute value < 40% and quantified by frequency, duration, and area under the curve per hour of NIRS monitoring (AUC rate, rScO2^*min/h). The primary outcome was ABI, defined as abnormalities noted on brain computerized tomography (CT) or magnetic resonance imaging (MRI) obtained during or after ECMO therapy. Results: Eighteen of Twenty patients who underwent NIRS monitoring while on VA ECMO were included in analysis. Eleven patients (61%) experienced rScO2 desaturations. Patients with desaturations were more frequently female (73 vs. 14%, p = 0.05), had acute liver dysfunction (64 vs. 14%, p = 0.05), and higher peak total bilirubin (5.2 mg/dL vs. 1.4 mg/dL, p = 0.02). Six (33%) patients exhibited ABI, and had lower pre-ECMO Glasgow Coma Scale (GCS) scores (5 vs. 10, p = 0.03) and higher peak total bilirubin levels (7.3 vs. 1.4, p = 0.009). All ABI patients experienced rScO2 desaturation while 42% of patients without ABI experienced desaturation (p = 0.04). ABI patients had higher AUC rates than non-ABI patients (right hemisphere: 5.7 vs. 0, p = 0.01, left hemisphere: 119 vs. 0, p = 0.06), more desaturation events (13 vs. 0, p = 0.05), longer desaturation duration (2:33 vs. 0, p = 0.002), and more severe desaturation events with rScO2 < 40 (9 vs. 0, p = 0.05). Patients with ABI had lower GCS scores (post-ECMO initiation) before care withdrawal or discharge than those without ABI (10 vs. 15, p = 0.02). Conclusions: The presence and burden of cerebral desaturations noted on NIRS cerebral oximetry are associated with secondary neurologic injury in adults undergoing VA ECMO.

In vivo validation of cerebral near-infrared spectroscopy: a review

We summarize the available in vivo validation of cerebral near-infrared spectroscopy (NIRS) oximetry to inform future in vivo validation strategies. In particular, to establish a way forward in the assessment of NIRS instrumentation for future randomized trials, a systematic literature search is performed. The records are screened and abstracts are assessed to select studies fulfilling our inclusion criteria. Twenty-two pediatric and 28 adult studies are analyzed after exclusion of three articles in each group. All studies compare regional cerebral tissue oxygenation measured by cerebral NIRS to invasive measurement of central or jugular venous oxygen saturation. In studies without Bland-Altman plots, we extracted data from scatter plots enabling estimation of mean difference (MD), standard deviation (SD), and limits of agreement (LOA). To assess the agreement between rStO 2 (regional cerebral tissue oxygenation) estimated by NIRS and by blood samples, weighted averages of the MDs and SDs from each study are calculated. We found a fair agreement between the overall mean of cerebral tissue oxygenation and the mean of a reference value measured by co-oximetry whatever NIRS instrument or site of blood sampling used. Cerebral oxygenation overestimates the reference at low values, some instruments apparently more than others. Thus, a high degree of scatter and a lack of a good reference method complicate in vivo validation of NIRS. It is difficult to draw any firm conclusions despite the large number of studies, and the result of this review leaves us questioning if more of such validation studies of cerebral NIRS oximetry are really needed. Furthermore, the combination of lack of validation and poor repeatability is an important issue when designing a randomized clinical trial of implementing cerebral NIRS oximetry into clinical care.

In vivo precision assessment of a near-infrared spectroscopy-based tissue oximeter (OxyPrem v1.3) in neonates considering systemic hemodynamic fluctuations

The aim was to determine the precision of a noninvasive near-infrared spectroscopy (NIRS)-based tissue oximeter (OxyPrem v1.3). Using a linear mixed-effects model, we quantified the variability for cerebral tissue oxygenation (StO2) measurements in 35 preterm neonates to be 2.64%, a value that meets the often-articulated clinicians' demand for a precise tissue oxygenation measurement. We showed that the variability of StO2 values measured was dominated by spontaneous systemic hemodynamic fluctuations during the measurement, meaning that precision of the instrument was actually even better. Based on simultaneous and continuous measurements of peripheral arterial oxygenation and cerebral StO2 with a second sensor, we were able to determine and quantify the physiological instability precisely. We presented different methods and analyses aiming at reducing this systematic physiological error of in vivo precision assessments. Using these methods, we estimated the precision of the OxyPrem tissue oximeter to be   ≤  1.85  %  . With our study, we deliver relevant information to establish highly precise cerebral oxygenation measurements with NIRS-based oximetry, facilitating the further development toward a substantially improved diagnosis and treatment of patients with respect to brain oxygenation.

Neural Mechanisms of Qigong Sensory Training Massage for Children With Autism Spectrum Disorder: A Feasibility Study

OBJECTIVES

Despite the enormous prevalence of autism spectrum disorder (ASD), its global impact has yet to be realized. Millions of families worldwide need effective treatments to help them get through everyday challenges like eating, sleeping, digestion, and social interaction. Qigong Sensory Training (QST) is a nonverbal, parent-delivered intervention recently shown to be effective at reducing these everyday challenges in children with ASD. This study tested the feasibility of a protocol for investigating QST's neural mechanism.

METHODS

During a single visit, 20 children, 4- to 7-year-old, with ASD viewed images of emotional faces before and after receiving QST or watching a video (controls). Heart rate variability was recorded throughout the visit, and power in the high frequency band (0.15-0.4 Hz) was calculated to estimate parasympathetic tone in 5-s nonoverlapping windows. Cerebral oximetry of prefrontal cortex was recorded during rest and while viewing emotional faces.

RESULTS

95% completion rate and 7.6% missing data met a priori standards confirming protocol feasibility for future studies. Preliminary data suggest: (1) during the intervention, parasympathetic tone increased more in children receiving massage (M = 2.9, SD = 0.3) versus controls (M = 2.5, SD = 0.5); (2) while viewing emotional faces post-intervention, parasympathetic tone was more affected (reduced) in the massage group (p = 0.036); and (3) prefrontal cortex response to emotional faces was greater after massage compared to controls. These results did not reach statistical significance in this small study powered to test feasibility.

DISCUSSION/CONCLUSION

This study demonstrates solid protocol feasibility. If replicated in a larger sample, these findings would provide important clues to the neural mechanism of action underlying QST's efficacy for improving sensory, social, and communication difficulties in children with autism.

Regional cerebral tissue oxygen saturation changes following blood transfusion in neuro-intensive care unit patients - a pilot observational study

BACKGROUND

Although central venous oxygen saturation (ScvO₂ ) is used to decide on red blood cell (RBC) transfusion, whether its improvement is associated with parallel improvement in cerebral oxygenation is not adequately studied. This study looked at changes in regional cerebral tissue oxygen saturation (rSO₂ ) following RBC transfusion in neuro-intensive care unit (ICU) patients.

METHODS

In this prospective observational pilot study, rSO₂ was measured in adult neuro-ICU patients before RBC transfusion, at the end and at 6, 12, 18 and 24 h after RBC transfusion. rSO₂ measurements were taken using cerebral oximetry on both sides of the hemicraniums. Haemoglobin, central venous pressure, ScvO₂ and temperature were recorded during the study period. Arterial oxygen content, central venous oxygen content and cerebral fractional oxygen extraction were calculated. Mann Whitney U test was used to study the changes in variables at baseline and at 24 h following RBC transfusion. Friedman's test was used to study changes in parameters from baseline to 24 h post-transfusion. A P value of <0·05 was considered to be significant.

RESULTS

The data from 13 subjects were analysed. rSO₂ increased significantly following RBC transfusion on both sides of the brain (P = 0·002, P = 0·007), with a corresponding decrease in cerebral fractional oxygen extraction (P = 0·001, P = 0·007).

CONCLUSIONS

RBC transfusion increased rSO₂ significantly on both sides of the brain. As patients' outcomes were not studied, whether this increase in regional cerebral oxygen saturation is beneficial or if it is because of excess DO₂ is still unclear. Further studies are required to clarify this issue.